Protein is an important part of a healthy diet. Now scientists have identified a taste receptor that may play a part in making sure we consume enough of it. According to a report published online yesterday by the journal Nature, the receptor responds to the taste of amino acids, the building blocks of protein.

Charles Zuker of the University of California, San Diego and colleagues discovered and tested the receptor, dubbed T1R1+3, in both mice and humans. In both species, the team found that the receptor responded to most of the 20 standard amino acids but did not react to similar natural and artificial compounds. "Our results," the authors write, "demonstrate that T1R1 and T1R3 combine to function as a broadly tuned amino acid receptor." In humans, T1R1+3 is more sensitive to the chemical glutamate than to any other amino acid. A related molecule, monosodium glutamate (MSG), is responsible for evoking the umami taste.

The researchers further determined that the genes for T1R1 and T1R3, which make up the new receptor, display individual variation. Such differences, they note, could account for subjective differences in the sense of taste.